Quick question, hoping someone could help me out. I have on a 2.8" pulley with 45lb/hr injectors, one step colder ngk plugs, and tuned using maf-t. car runs fine, has been for around 8 months now. all of a sudden this morning the car stutters and hesitates under accelearation and low rpms. Any ideas what it could be? Feels like a bad plug or wire or something. My first thought was that the colder plugs might be too cold with this cold weather in NJ. Please help!

 

just in case anyone cared I figured out the problem...I think.

I pulled out the plugs. Three were dark, one was light. I am assuming that the one cylinder was running lean. Again assuming this was because the spark wasn't hot enough (cold plugs + SUPER cold weather) so the fuel was not igniting properly producing a lean cylinder. I popped back in the stock NGK plugs and the car runs fine. So here is a warning to all you guys running the NGK bkr7e's in the cold weather.

 

Wouldn't a lack of fuel ignition create a rich environment?

 

Yeah, if would. The three dark plugs were probably what you were feeling. They should all have a nice even brown color. Too dark or black is excess fuel sitting on the plugs. Still, that shouldn't happen with the coil pack setup on these cars. Maybe try letting the car warm up a little more next time, if not look for an airflow restriction or something. Misfires should also store codes in the PCM, and possibly turn on the CEL.

edit: Oh, and I missed the fact that you are using a Maf-t. The Maf adjusts the a/f based on the readings of the stock mass air sensor. Since it it a percentage, it will change more than it should when the weather changes. That is most likely the cause of your problem.

 

yeah if you got 3 coated plugs and 1 light, ya might wanna check for either lost spark on that plug or injector malfunction...no CEL?

 

yea, it threw a cel, but for some reason my OBDII port is not getting power. I tried two different scanners and neither of them read anything from the port. I'm thinking thats a completely different problem.

but again, i threw in the stock plugs and the car runs fine. i normally warm up the car for a good 20 minutes before i leave for work and would sputter even when warming up. but you guys are right about the maf-t. i completely forgot that it would change that much in colder weather. unfortunately i sold my wideband so i have no way of monitoring the a/f ratio aside from checking the plugs to see if they are lean or rich. thanks again.

 

OOO, no power to the data line, a definate problem. you might have just had a bad diode on the plug. what were they gapped at?

 

i think the colder plugs were gapped at .40 if I remember correctly.

 

i really wish i knew what code you were throwing cause i guarentee its a p0301 or 300.
so if its running fine with the stock plugs (stock gap being .45 of course) back in it, that makes me wonder about the engine and how much gap it was wanting at what every the air temp was at. or if the plug itself was just bad or the plug wire wasnt seated right maybe having wiggled itself loose...argh, so many things it COULD be...

 

the car running rich causes the computer to toss a lean code more often the n not.

 

yeah but what he is describing sounds like a mix of a misfire with the stuttering. it could throw a lean code as well...but i would expect to see a misfire code on cylinder one more than anything.

 

there is a place by me that is great with that stuff and I am going to have them check out the OBDII port and then run it over to AutoZone for a free scan. I will post up codes when I get them. Thanks for the help guys.

 

I am having a similar problem but it only occurs in temperatures below 40degrees farenheit and only around 5K rpm and higher.

The vehicle literally goes nuts and won't accelerate.

I changed my plugs back to stock and the problem seemed to go away but now its back again. This may seem crazy but i actually think it may be my cold air intake!!!!

 

Pull your o2 sensor, like the clip on it, i bet your car runs way better, mine has since i did earlier today

 

there are a number of factors that could potentially be contributing to this and you wont' be able to tell unless you check things like your plugs, a/f ratio, injectors, or anything else that might be awry.
the cold weather does wonders on forced induction cars. the cold air is great! but you have to tune your car accordingly. if you are using a maf-t to tune, your setting must change in this cold weather.
other than that, you could have a bad coil pack if its only one cylinder fouling a plug. the o-ring on an injector could be cracked or broken and you could be leaking fuel so under wot you run lean in a cylinder or two.
there could be a number of other things. i would check your a/f with a wideband if you can. other than that, check your plugs and see if its only one cylinder giving your problems. if not, check your injectors.




excellent idea!